High-performance bonding-controllable prestressed component

Abstract

The invention discloses a high-performance bonding-controllable prestressed member which comprises a heating assembly and a prestressed tendon applied to a concrete part, and the prestressed tendon comprises a sleeve arranged in the concrete part; the steel strand is arranged in the sleeve and extends in the axial direction of the sleeve, a gap is formed between the steel strand and the inner wall of the sleeve, the tensile strength of the steel strand reaches 2160 Mpa or above, the stress corrosion resistance reaches the minimum value of 2 hours, and the stress corrosion resistance reaches the median value of 5 hours or above; the controllable bonding layer is arranged in the gap between the sleeve and the steel strand, and the heating assembly is used for heating and curing the controllable bonding layer. According to the prestressed member, high corrosion resistance of the ultrahigh-strength prestressed steel strand can be achieved, the external sleeve of the steel strand can be further effectively protected and prevented from corrosion, the service life is remarkably prolonged, the curing time of the controllable bonding material is controllable, the prestressed tendons can be rapidly cured after being tensioned, the curing waiting period is shortened, the project progress can be accelerated, and the construction efficiency is improved. And the structural safety is improved.

Description

Technical Field

[0001] This application belongs to the technical field of prestress, and specifically relates to a prestressed member with high performance and controllable bonding. Background Art

[0002] The durability of prestressing tendons has an important impact on the performance of prestressed structures. Therefore, the durability assurance rate of prestressing tendons should be higher than that of ordinary steel bars. Especially when the structure is under the action of a complex environment, simply improving the material quality and thickness of the concrete cover often cannot ensure the design service life. With the increase in the strength level of steel strands, their stress corrosion sensitivity in a high-stress environment increases significantly, which is not conducive to the application of ultra-high-strength steel strands.

[0003] Especially in the field of wind power technology, the current prestressed members such as anchor bolts or high-strength screw rods used in the foundations of wind turbines are all unbonded prestressed structures. Generally, they are coated with dacromet on their outer surfaces for anti-corrosion. During specific use, a PVC pipe is generally sleeved on the outer surfaces of the anchor bolts and high-strength screw rods, so that the anchor bolts and high-strength screw rods are in an unbonded state with the concrete. After tensioning, a sealing treatment is performed on the top of the PVC pipe to prevent water from entering the PVC pipe. Usually, the waterproof sealing treatment process at the top of the PVC pipe is complex and has defects, and rainwater can enter the PVC pipe. Since dacromet loses its anti-corrosion ability when it encounters water, the prestressed members of the foundation constructed by the current scheme are severely corroded, seriously threatening the safety of wind turbine units. Currently, the wind turbine tower mainly adopts an external prestressed structure and a prestressed cable form. The external prestressed tendons used are directly in contact with the external environment, especially in a relatively harsh corrosion environment such as by the sea. Therefore, it is urgent to improve the adaptability and corrosion resistance of the key component of the prestressing tendons in the use environment and extend their service life. Summary of the Invention

[0004] The purpose of this application is to provide a prestressed member with high performance and controllable bonding to solve the technical problem that the existing prestressing tendons have low corrosion resistance and cannot ensure the design service life.

[0005] To achieve the above purpose, the first aspect of this application provides a prestressed member with high performance and controllable bonding, including a heating component and a prestressing tendon applied in a concrete member. The prestressing tendon includes:

[0006] A casing arranged in the concrete member;

[0007] A steel strand arranged inside the casing. The steel strand extends along the axial direction of the casing, and there is a gap between the steel strand and the inner wall of the casing. The tensile strength of the steel strand reaches 2160 Mpa or more, and the minimum value of the stress corrosion test time of the steel strand in Solution A reaches 2 hours or more, and the median value reaches 5 hours or more;

[0008] A controllable bonding layer disposed at the gap between the casing and the steel strand;

[0009] Wherein, the heating assembly is used to heat and cure the controllable bonding layer.

[0010] Wherein, the stress corrosion test is carried out in accordance with the provisions of the current national standard "Test Methods for Steel for Prestressed Concrete" GB / T 21839.

[0011] In one or more embodiments, the controllable bonding layer is an epoxy resin layer, and the controllable bonding layer uniformly fills the gap between the steel strand and the casing. The thickness of the controllable bonding layer in the radial direction of the steel strand is 1.15 - 1.25 mm.

[0012] In one or more embodiments, the steel strand is obtained by stranding 19 wire rods, the nominal diameter of the steel strand is 21.8 - 28.6 mm, and the nominal area of the steel strand is 313 - 532 mm 2 .

[0013] In one or more embodiments, the steel strand is obtained by stranding 7 wire rods, the nominal diameter of the steel strand is 15.2 - 21.6 mm, and the nominal area of the steel strand is 140 - 285 mm 2 .

[0014] In one or more embodiments, the heating assembly includes a power source electrically connected to the steel strand.

[0015] In one or more embodiments, the steel strand includes tensioning ends at both ends, the tensioning ends extend out of the casing and the concrete member, and the power source is connected to the two tensioning ends of the steel strand.

[0016] In one or more embodiments, it includes at least two spaced-apart prestressing tendons. The steel strand of each prestressing tendon includes a tensioning end at one end and an anchoring end at the other end. The anchoring end and the tensioning end extend out of the casing. The anchoring end is fixed inside the concrete member, and the tensioning end extends out of the concrete member;

[0017] The heating assembly further includes a conductive fixture, the conductive fixture is located inside the concrete member and connects the anchoring ends of adjacent steel strands;

[0018] Wherein, the power source is connected to the tensioning ends of adjacent steel strands.

[0019] In one or more embodiments, the conductive fixture is a U-shaped conductive fixture, and the conductive fixture is clamped and fixed between the adjacent anchoring ends of the steel strands.

[0020] In one or more embodiments, the heating component further includes a variable resistor arranged on the connection circuit between the power supply and the steel strand.

[0021] In one or more embodiments, a plurality of longitudinal ribs distributed in a ring shape and a plurality of transverse ribs arranged at intervals along the axial direction of the sleeve are formed on the outer wall of the sleeve. The longitudinal ribs extend along the axial direction of the sleeve, the transverse ribs extend along the circumferential direction of the sleeve, and each transverse rib connects the plurality of longitudinal ribs.

[0022] In one or more embodiments, the steel strand is obtained by stranding a plurality of wire rods. The rate of sorbitization of the wire rod is greater than or equal to 95%, the spacing of the sorbitic lamellae is 50 - 70 nm, and the chemical composition of the wire rod in mass percentage includes:

[0023] C 0.85 - 0.91%, Si 0.3 - 1.0%, Mn 0.2 - 0.8%, Cr 0.15 - 0.45%, V 0.02 - 0.05%, S less than or equal to 0.008%, P less than or equal to 0.010%, N less than or equal to 0.004%, O less than or equal to 0.0020%, and the balance is Fe and other inevitable impurities.

[0024] In one or more embodiments, the steel strand is prepared by the following steps:

[0025] Smelt molten steel to obtain target molten steel. The chemical composition of the target molten steel in mass percentage includes: C 0.85 - 0.91%, Si 0.3 - 1.0%, Mn 0.2 - 0.8%, Cr 0.15 - 0.45%, V 0.02 - 0.05%, S less than or equal to 0.008%, P less than or equal to 0.010%, N less than or equal to 0.004%, O less than or equal to 0.0020%, and the balance is Fe and other inevitable impurities;

[0026] Adopt small billet continuous casting to cast the target molten steel into shape to obtain an intermediate billet;

[0027] Perform a high-speed wire rolling process on the intermediate billet to obtain a coiled bar;

[0028] Immediately immerse the coiled bar into a salt bath tank for on-line salt bath isothermal treatment. After the treatment is completed, immediately put the coiled bar into a heat preservation corridor for on-line aging for temperature control treatment. After the treatment is completed, cool it to room temperature to obtain the wire rod;

[0029] The multiple wire rods are sequentially subjected to pickling, phosphating, drawing, stranding and stabilizing processes to obtain the steel strand;

[0030] Among them, the salt bath temperature of the on-line salt bath isothermal treatment is 530-560 °C, the salt bath time is 100-250 s, and the average cooling rate of the temperature control treatment is not higher than 0.2 °C / s.

[0031] Different from the prior art, the beneficial effects of this application are:

[0032] The prestressed component of this application realizes the high corrosion resistance of the ultra-high-strength prestressed steel strand. By further effectively protecting and anti-corrosive the external casing of the steel strand, its service life is significantly extended. At the same time, the curing time of the controllable bonding material of the prestressed component is controllable. After the controllable bonded prestressed tendon is tensioned, it can be quickly cured, greatly shortening the curing waiting period, which is beneficial to accelerating the project progress and improving the structural safety;

[0033] By optimizing the chemical composition ratio of the wire rod, reasonable preparation process parameters and post-rolling controlled cooling process, this application significantly improves the strength and plasticity of the wire rod and the homogeneity of the steel, so that it can obtain an ultra-high strength of more than 2300 MPa by drawing with a smaller area reduction rate in the subsequent steel strand preparation process, reducing the area reduction rate of drawing and significantly improving the plasticity index of the wire rod, which can reduce the surface damage and internal defects of the wire rod during subsequent drawing processing, thereby improving the stress corrosion index of the steel strand;

[0034] The sorbitization rate of the wire rod of the steel strand of this application reaches 95%, the sorbitic lamellar spacing is 50-70 nm, and the tensile strength reaches more than 1425 Mpa; the tensile strength of the steel strand of this application reaches more than 2300 Mpa, which is beneficial to carbon emission reduction and material consumption reduction, and at the same time has excellent stress corrosion resistance. Taking the prepared 1×7 steel strand as an example, the minimum value of stress corrosion is 2.5 hours and the median value is 5 hours, which is significantly higher than the minimum value of 0.7 hours and the median value of 1.2 hours recommended by the existing corresponding ultra-high strength related standards. Based on the existing standard to meet the design service life requirement of 50 years, using the prestressed tendon of this application, its service life can be estimated to reach about 175 years according to the corrosion-resistant time;

[0035] With the increase of the strength level of the steel strand, its stress corrosion sensitivity in a high-stress environment increases significantly. This application clarifies the applicability of steel strands with different strength levels in corrosive media, avoids sacrificing durability due to strength increase, and enhances the positive role of ultra-high-strength materials in energy conservation and carbon reduction. Description of the Drawings

[0036] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0037] Figure 1 It is a schematic structural diagram of an embodiment of the high-performance controllable-bonding prestressed member of the present application;

[0038] Figure 2 It is a schematic cross-sectional structural diagram of an embodiment of the prestressing tendon of the present application;

[0039] Figure 3 It is a schematic structural diagram of another embodiment of the high-performance controllable-bonding prestressed member of the present application;

[0040] Figure 4 It is a schematic flow diagram of the preparation method of the steel strand of the present application;

[0041] Figure 5 It is a metallographic structure picture of the wire rod prepared in Example 1 of the present application;

[0042] Figure 6 It is a metallographic structure picture of the wire rod prepared in Example 2 of the present application;

[0043] Figure 7 It is a metallographic structure picture of the wire rod prepared in Example 3 of the present application.

[0044] As shown in the figure:

[0045] Prestressing tendon 100; sleeve 101; transverse rib 1011; longitudinal rib 1012; steel strand 102; wire rod 1021; tension end 1022; anchorage end 1023; controllable bonding layer 103;

[0046] Heating assembly 200; power supply 201; variable resistor 202; conductive fixture 203. Detailed implementation manners

[0047] In order to enable those skilled in the art to better understand the technical solutions in the present application, the following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0048] To solve the technical problem that the existing prestressed tendons have low corrosion resistance and cannot guarantee the designed service life, the applicant has developed a new type of prestressed component. This prestressed component enables ultra-high-strength prestressed steel strands to have high stress corrosion resistance and further effectively protects and anticorrosives the external casing of the steel strands, which can significantly extend its service life, facilitate carbon emission reduction and material consumption reduction, and at the same time is conducive to accelerating the project progress and improving the structural safety.

[0049] Specifically, please refer to Figure 1 , Figure 1 which is a schematic structural diagram of an embodiment of the high-performance controllable bond prestressed component of the present application.

[0050] As Figure 1 shown, the prestressed component includes a heating assembly 200 and a prestressed tendon 100 applied in a concrete member 300. The prestressed tendon 100 includes a casing 101 arranged in the concrete member and a steel strand 102 arranged inside the casing 101.

[0051] Among them, the steel strand 102 is arranged to extend along the axial direction of the casing 101, and a gap is formed between the steel strand 102 and the inner wall of the casing 101.

[0052] The prestressed component further includes a controllable bond layer 103 arranged at the gap between the casing 101 and the steel strand 102, and the heating assembly 200 is used to heat and cure the controllable bond layer 103.

[0053] It can be understood that by wrapping the steel strand 102 with the controllable bond layer 103, the steel strand 102 can be effectively protected from corrosion, thereby extending its service life.

[0054] To ensure the protection effect, in this embodiment, the controllable bond layer 103 can be an epoxy resin layer, and the controllable bond layer 103 evenly fills the gap between the steel strand 102 and the casing 101. The thickness of the controllable bond layer 103 in the radial direction of the casing 101 is 1.15 - 1.25 mm.

[0055] Specifically, in one embodiment, a one-component epoxy resin obtained by mixing epoxy resin, heat-induced latent curing agent, modifier, and filler can be injected into the gap between the steel strand 102 and the casing 101, and after curing, the controllable bond layer 103 is formed.

[0056] In this embodiment, a heating component 200 is also arranged to accelerate the curing of the controllable bonding layer 103 by heating it, thereby significantly improving the fixing speed of the controllable bonding layer 103. During construction, the controllable bonding material can be filled into the gap between the steel strand 102 and the sleeve 101. After that, a post-tensioning process is performed on the steel strand 102. After the tensioning is completed, the controllable bonding material is quickly heated to cure and form a controllable bonding layer 103 that completely wraps the steel strand 102.

[0057] Specifically, in this embodiment, both ends of the steel strand 102 extend out of the concrete member 300, so that tensioning ends 1022 are formed at both ends of the steel strand 102. During the post-tensioning process, the steel strand 102 can be tensioned through the tensioning ends 1022 at both ends.

[0058] The heating component 200 may include a power supply 201 electrically connected to the two tensioning ends 1022 of the steel strand 102. Through the power supply 201, a low-voltage and high-current can be passed into the steel strand 102 to heat the steel strand 102 and transfer the heat to the controllable bonding material to accelerate its curing.

[0059] To control the heating current, in this embodiment, the heating component 200 further includes a variable resistor 202 arranged on the connection circuit between the power supply 201 and the steel strand 102. By adjusting the size of the variable resistor 202, the heating current can be controlled, and thus the heating of the controllable bonding material can be accurately controlled.

[0060] In this embodiment, the sleeve 101 can be a plastic sleeve 101. To improve its strength, please refer to Figure 1 and Figure 2 , Figure 2 is a cross-sectional structural schematic diagram of an embodiment of the prestressed tendon 100 of the present application. As Figure 1 and Figure 2 shown, two longitudinal ribs 1012 distributed at 180° and a plurality of transverse ribs 1011 arranged at intervals along the axial direction of the sleeve 101 are formed on the outer wall of the sleeve 101. The longitudinal ribs 1012 extend along the axial direction of the sleeve 101, the transverse ribs 1011 extend along the circumferential direction of the sleeve 101, and each transverse rib 1011 connects a plurality of longitudinal ribs 1012, thereby significantly improving the strength of the sleeve 101.

[0061] It should be understood that in other embodiments, the number of longitudinal ribs 1012 and the number of transverse ribs 1011 can be adjusted based on actual needs, or only longitudinal ribs 1012 can be provided, or only transverse ribs 1011 can be provided, and the effects of this embodiment can be achieved to a certain extent.

[0062] Further, please refer to Figure 2, in this embodiment, the specification of the steel strand 102 is 1*19, that is, it is obtained by stranding 19 wire rods 1021. The nominal diameter of the steel strand 102 is 21.8 - 28.6 mm, and the nominal area of the steel strand 102 is 313 - 532 mm 2 .

[0063] In other embodiments, the steel strand 102 can also be obtained by stranding other numbers of wire rods 1021. For example, the specification of the steel strand 102 can also be 1*7, that is, it is obtained by stranding 7 wire rods 1021. The nominal diameter of the steel strand can be 15.2 - 21.6 mm, and the nominal area of the steel strand can be 140 - 285 mm 2 , and it can also achieve the effects of this embodiment.

[0064] In this embodiment, the stress corrosion resistance of the steel strand 102 reaches a minimum of 2 hours or more and a median of 5 hours or more.

[0065] Specifically, the stress corrosion resistance reaching a minimum of 2 hours or more and a median of 5 hours or more means that when the steel strand of this embodiment is subjected to a stress corrosion test with reference to Standard GB / T 15970.6 - 2007, the minimum test time in Solution A reaches 2 hours or more and the median reaches 5 hours or more.

[0066] In the above - mentioned embodiment, the prestressing tendon 100 adopts a double - end tensioning form, and both ends of the steel strand 102 extend out of the concrete member 300; in another embodiment, the prestressing tendon 100 can also adopt a single - end tensioning form, and the steel strand 102 can also extend out of the concrete member 300 only at one end. Please refer to Figure 3 , Figure 3 which is a schematic structural diagram of another embodiment of the high - performance controllable bond prestressed member of this application.

[0067] As Figure 3 shown, this prestressed member includes two prestressing tendons 100. The steel strand 102 of each prestressing tendon 100 includes a tensioning end 1022 at one end and an anchoring end 1023 at the other end. The anchoring end 1023 and the tensioning end 1022 extend out of the sleeve 101. The anchoring end 1023 is fixed inside the concrete member 300, and the tensioning end 1022 extends out of the concrete member 300.

[0068] In this embodiment, the heating component 200 further includes a conductive fixture 203. The conductive fixture 203 is located inside the concrete member 300 and connects the anchoring ends 1023 of adjacent steel strands 102.

[0069] Specifically, in this embodiment, the conductive fixture 203 is a U - shaped conductive fixture 203, and the conductive fixture 203 is clamped and fixed between the anchoring ends 1023 of adjacent steel strands 102.

[0070] In this embodiment, the power supply 201 is arranged at the tension end 1022 of the adjacent steel strands 102, so that a loop can be formed, and the controllable bonding materials of the two prestressing tendons 100 can be heated and cured simultaneously.

[0071] Based on the prestressed components of the above embodiments, the steel strands 102 can be effectively protected, and their service life can be significantly extended. At the same time, the curing time of the controllable bonding material of the prestressed component is controllable. After the controllable bonded prestressing tendon 100 is tensioned, it can be quickly cured, greatly shortening the curing waiting period, which is beneficial to accelerating the project progress and improving the structural safety.

[0072] In order to further improve the stress corrosion resistance of the prestressing tendon and increase the strength of the prestressing tendon, the material and preparation method of the steel strand in this application are further improved. Specifically, the chemical composition of the wire rod of the steel strand in this application includes, by mass percentage:

[0073] C 0.85 - 0.91%, Si 0.3 - 1.0%, Mn 0.2 - 0.8%, Cr 0.15 - 0.45%, V 0.02 - 0.05%, S less than or equal to 0.008%, P less than or equal to 0.010%, N less than or equal to 0.004%, O less than or equal to 0.0020%, and the balance is Fe and other inevitable impurities.

[0074] By optimizing the mass fractions of the chemical components of the wire rod in this application, the homogeneity of the steel is significantly improved, and the stress corrosion index of the steel is improved.

[0075] Specifically, in this application, the C content is limited to 0.85 - 0.91% to ensure a relatively high tensile strength of the wire rod; by limiting the Si content to 0.3 - 1.0%, it helps to improve the corrosion resistance and relaxation resistance of the steel; by limiting the Mn content to 0.2 - 0.8%, the strength and hardenability of the steel can be improved, ensuring a good work hardening rate of the wire rod; by limiting the Cr content to 0.15 - 0.45%, on the one hand, it is beneficial to obtain retained austenite, on the other hand, it forms a dense oxide film on the steel surface, and at the same time avoids the difficulty of controlling segregation caused by too much Cr content; by limiting the V content to 0.02 - 0.05%, the carbon oxides formed by V act as effective hydrogen traps in the steel, improving the stress corrosion index of the steel.

[0076] In addition, in order not to affect the strength and plasticity of the steel, in this application, the S content is limited to less than or equal to 0.008%, the P content is limited to less than or equal to 0.010%, the N content is limited to less than or equal to 0.004%, and the O content is limited to less than or equal to 0.0020%.

[0077] Based on the above content ratio, while ensuring the high strength of the wire rod, its stress corrosion resistance can be significantly improved. In one embodiment, the diameter of the wire rod can reach 8 - 14 mm, the tensile strength can reach 1470 - 1570 Mpa, and the reduction of area can be 35 - 48%.

[0078] The present application also provides a method for preparing a steel strand. Please refer to Figure 4 , Figure 4 which is a schematic flow chart of the method for preparing the steel strand of the present application.

[0079] As Figure 4 shown, the preparation method includes:

[0080] S100. Smelt molten steel to obtain target molten steel.

[0081] Among them, the chemical composition of the target molten steel is the same as that of the wire rod, which will not be elaborated here, so that the wire rod with the target chemical composition can be prepared based on the target molten steel.

[0082] In one embodiment, the step of smelting molten steel can be specifically carried out in sequence with converter smelting and LF furnace refining.

[0083] Among them, converter smelting is specifically to send molten iron into the converter to be mixed with scrap steel to form molten steel, and carry out desiliconization, dephosphorization, and oxygen blowing decarburization. When tapping, alloys are added to the ladle for deoxidation alloying;

[0084] LF furnace refining is specifically to send the molten steel after converter smelting into the LF refining furnace for chemical composition adjustment, temperature control, and regulate the inclusions in the molten steel through soft stirring until the temperature of the molten steel reaches the continuous casting requirement and the chemical composition of the molten steel meets the standard, and then tap to obtain the target molten steel.

[0085] S200. Adopt small billet continuous casting to cast the target molten steel into a shape to obtain an intermediate billet.

[0086] When the target molten steel with the temperature and chemical composition meeting the requirements is prepared, the target molten steel can be cast into a shape by using the continuous casting process.

[0087] In one embodiment, the size of the small billet for continuous casting can be 180 mm × 240 mm; in other embodiments, the size of the small billet can also be adjusted based on actual needs, and the effects of this embodiment can be achieved.

[0088] To ensure the tensile strength and stress corrosion resistance of the prepared wire rod, the parameters of the continuous casting process are optimized in this application. Specifically, in one embodiment, the superheat of the target molten steel can be 20 - 25°C, the stirring current of the mold can be 270 ± 25 A, the stirring frequency of the mold can be 3 ± 0.5 Hz, the drawing speed during continuous casting can be 1.2 ± 0.05 m / min, the specific water consumption during continuous casting can be 0.22 ± 0.01 L / kg, the stirring current at the end can be 450 ± 25 A, the stirring frequency at the end can be 8 ± 0.5 Hz, and the total reduction of soft reduction can be 15.0 ± 0.2 mm.

[0089] S300. Perform a high-speed wire rolling process on the intermediate billet to obtain a coil.

[0090] Among them, the high-speed wire rolling process specifically involves heating the intermediate billet and then sequentially performing rough rolling, finish rolling, and spinning to obtain a coil.

[0091] In one embodiment, the heating temperature can be 1080 - 1150°C, the starting rolling temperature of rough rolling can be 950 - 1000°C, and the entry temperature of finish rolling can be 840 - 900°C.

[0092] To facilitate the effect of subsequent controlled cooling after rolling, the spinning temperature can be 840 - 900°C.

[0093] S400. Immediately immerse the coil in a salt bath tank for on-line salt bath isothermal treatment. After the treatment is completed, immediately transfer the coil to a heat preservation corridor for on-line aging for temperature control treatment. After the treatment is completed, cool it to room temperature to obtain a wire rod.

[0094] After the high-speed wire rolling process, at this time, the coil still maintains the spinning temperature of the rolling process. Without uncoiling, directly immerse the coil in the salt bath tank immediately to achieve on-line salt bath isothermal treatment, and precisely control the material structure and properties.

[0095] Compared with the traditional off-line salt bath heat treatment, the solution of this application does not require uncoiling the coil for heat treatment and then recoiling, avoiding surface damage to the steel, and thus helping to improve the stress corrosion index of the steel strand.

[0096] In one embodiment, the salt bath temperature for on-line salt bath isothermal treatment can be 530 - 560°C, and the salt bath time can be 100 - 250 s.

[0097] After on-line salt bath isothermal treatment, the coil can be immediately transferred to a heat preservation corridor for on-line aging to precisely control the temperature of the coil, and thus refine the microstructure of the steel.

[0098] In one embodiment, the average cooling rate of the temperature control treatment is not higher than 0.2°C / s.

[0099] The post-rolling controlled cooling process based on online salt bath isothermal treatment and online aging in the heat preservation corridor can refine the microstructure of the wire rod and significantly increase the rate of sorbitization to improve the strength and plasticity of the wire rod.

[0100] S500. The stranded wire is prepared by successively passing multiple wire rods through pickling, phosphating, drawing, stranding, and stabilizing processes.

[0101] In one embodiment, pickling is specifically carried out by pickling the coil in a 15 - 20 wt% hydrochloric acid solution for 7 - 10 min at a pickling temperature of 35 - 42 °C, which not only ensures the complete removal of hot-rolled scale but also avoids excessive hydrogen absorption by the wire rod.

[0102] In one embodiment, phosphating is specifically carried out 20 - 28 h after the pickled coil is placed.

[0103] In one embodiment, drawing is specifically carried out by drawing the coil in 9 - 11 passes with a reduction ratio of 23 - 25% per pass, a drawing speed not higher than 2 m / s, and a temperature rise not higher than 100 °C per pass.

[0104] Based on the post-rolling controlled cooling process of the above S400, the wire rod has high strength and plasticity. Therefore, the target strength can be achieved with a lower drawing reduction ratio, effectively reducing the surface damage and internal defects of the wire rod, thus contributing to improving the stress corrosion resistance.

[0105] In one embodiment, the tension during stranding can be greater than or equal to 80 KN, the speed can be less than or equal to 36 m / min, and the stabilizing temperature in the stabilizing process can be 400 - 430 °C.

[0106] Based on the wire rod and its preparation method of the above embodiments, by optimizing the chemical composition ratio of the wire rod, reasonable preparation process parameters, and post-rolling controlled cooling process, the strength and plasticity of the wire rod and the homogeneity of the steel are significantly improved, enabling it to obtain an ultra-high strength of more than 2300 MPa with a smaller reduction ratio during the subsequent preparation process of the stranded wire, reducing the drawing reduction ratio and significantly improving the plasticity index of the wire rod, which can reduce the surface damage and internal defects of the wire rod during subsequent drawing processing, thereby improving the stress corrosion index of the stranded wire.

[0107] The beneficial effects of the material and preparation method of the stranded wire in this application are further elaborated in detail below with specific examples.

[0108] Example 1:

[0109] A 1*7 stranded wire of 2300 - 2360 MPa grade is prepared by the following processes:

[0110] (1) Molten steel smelting process

[0111] The molten steel is smelted through the BOF smelting and LF refining steps in sequence to obtain the target molten steel. The chemical composition of the target molten steel is shown in Table 1 below by mass percentage;

[0112] Among them, in the BOF smelting step, hot metal is fed into the BOF and mixed with scrap steel to form molten steel, and desiliconization, dephosphorization, and oxygen blowing decarburization are carried out. When tapping, alloys are added to the ladle for deoxidation alloying;

[0113] In the refining step, the molten steel after BOF smelting is fed into the LF refining furnace for chemical composition adjustment, temperature control, and the inclusions in the molten steel are controlled by soft stirring. After the temperature and chemical composition meet the standards, tapping is carried out. Among them, the superheat of the target molten steel is 20°C.

[0114] (2) Continuous casting process

[0115] Small billet continuous casting is adopted to cast the target molten steel into small billets with a cross-sectional size of 180mm×240mm.

[0116] Among them, the superheat of the target molten steel is controlled at 20°C, the stirring current of the mold is 245A, the stirring frequency of the mold is 2.5Hz, the drawing speed during continuous casting is 1.15m / min, the specific water volume for continuous casting is 0.21L / kg, the terminal stirring current is 425A, the terminal stirring frequency is 7.5Hz, and the total reduction of soft reduction is 14.8mm.

[0117] (3) High-speed wire rolling process

[0118] The intermediate billet obtained from the continuous casting process is processed into wire rods with a diameter of 14mm through high-speed wire rolling. The heating temperature is 1150°C, the starting rolling temperature of rough rolling is 1000°C, the entry temperature of finish rolling is 850°C, and the laying head temperature is 850°C.

[0119] (4) Post-rolling controlled cooling process

[0120] The coiled wire after laying head is directly immersed in a salt bath tank for salt bath. The temperature of the salt bath tank is 530°C, and the salt bath time is 250s; the coiled wire after salt bath isotherm treatment immediately enters the heat preservation corridor for slow cooling, and the average cooling rate is 0.15°C / s.

[0121] (5) Steel strand processing process

[0122] The coiled wire is pickled, phosphated, and drawn to obtain wire rods, and then 2300-2360MPa grade steel strands are obtained through stranding and stabilization processes;

[0123] Among them, pickling is carried out with an aqueous solution of hydrochloric acid at a concentration of 19 wt%, pickling for 8 minutes, at a temperature of 35 °C. After pickling, the coiled bars are placed for 24 hours and then enter the phosphating process; drawing is carried out in 11 passes, with a reduction rate per pass of 23%, a drawing speed of 2 m / s, and a temperature rise of 100 °C per pass; the strand twisting tension is 80 kN, the speed is 36 m / min, and the stabilization temperature is 400 °C.

[0124] Examples 2 to 4:

[0125] A 1×7 steel strand with a strength level of 2300 - 2360 MPa is prepared in a manner substantially the same as in Example 1, except that: 1. The chemical composition content of the wire rods in Examples 2 to 4 is different from that in Example 1; 2. The parameters of each process in Examples 2 to 3 are different from those in Example 1.

[0126] The chemical composition content of the wire rods in Examples 1 to 4 can be seen in Table 1 below, and the process parameters in Examples 1 to 3 can be seen in Table 2 below.

[0127] Table 1

[0128]

[0129] Table 2

[0130]

[0131]

[0132] Effect Example 1:

[0133] The metallographic structure of the wire rods prepared in Examples 1 to 3 was detected. The detection method includes:

[0134] A wire rod with a length of 10 cm was taken from the head of the wire rod, made into a metallographic sample, observed by scanning electron microscopy after electrolytic polishing, and Figures 5 to 7 , Figure 5 is a metallographic structure picture of the wire rod prepared in Example 1 of this application, Figure 6 is a metallographic structure picture of the wire rod prepared in Example 2 of this application, Figure 7 is a metallographic structure picture of the wire rod prepared in Example 3 of this application.

[0135] It was found from the above detection that the structures of the wire rods in Examples 1 - 3 are all sorbite structures, and their metallographic data are as shown in Table 3 below. The rates of sorbitization in Examples 1 to 3 all reach 95%, and the sorbite lamellar spacing is 50 - 70 nm, indicating that the wire rods have excellent strength and toughness.

[0136] Table 3

[0137] Embodiment Diameter / mm Sorbite rate Grain boundary cementite Martensite 1 14 95 0.5 0.5 2 13 95 0 0 3 8 95 0 0

[0138] Effect Example 2:

[0139] The mechanical properties of the wire rods prepared in Examples 1 to 3 were tested using a tensile testing machine. The testing method referred to the standard test method and definition of GB / T 228, and the following data in Table 4 were obtained.

[0140] Table 4

[0141]

[0142] As can be seen from the above data, the tensile strength of the wire rods prepared in Examples 1 to 3 reached above 1425 Mpa, and the percentage elongation at fracture reached above 35%, showing significantly excellent mechanical properties.

[0143] Effect Example 3:

[0144] The strength of the steel strands prepared in Examples 1 to 3 was tested. The testing method referred to the standard GB / T 5224-2020, and the following data in Table 5 were obtained.

[0145] Table 5

[0146]

[0147] As can be seen from the data in the above table, the tensile strength of the steel strands in Examples 1 to 3 all reached above 2300 Mpa, having excellent properties and being able to meet the requirements of the new national standard.

[0148] Effect Example 4:

[0149] The stress corrosion resistance of the steel strands prepared in Examples 1 to 3 was tested. The testing method referred to the standard GB / T15970.6-2007, and the following data in Table 6 were obtained.

[0150] Table 6

[0151]

[0152] As can be seen from the above data, the steel strands prepared in Examples 1 to 3 all had excellent stress corrosion resistance. The minimum value of stress corrosion was 2.5 h, and the median was 5 h, far superior to the existing 2300 MPa steel strands. Based on the requirement of meeting the design service life of 50 years with the existing standard, using the prestressed tendons of this application, its service life can be estimated to reach about 175 years according to the corrosion-resistant time.

[0153] For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or basic characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present application is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present application. Any reference signs in the claims should not be construed as limiting the claims involved.

[0154] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-performance controllable bonded prestressed component, characterized in that: The invention comprises a heating assembly and a prestressed tendon applied to a concrete member, wherein the prestressed tendon comprises: a casing arranged in the concrete member; A steel strand is arranged inside the casing, the steel strand is extended along the axial direction of the casing, and a gap is formed between the steel strand and the inner wall of the casing, the tensile strength of the steel strand reaches 2160 MPa or more, and the minimum value of the stress corrosion test time of the steel strand in solution A reaches 2 hours or more, and the median value reaches 5 hours or more; A controllable bonding layer is arranged at a gap between the casing and the steel strand; Wherein, the heating component is used to heat and cure the controllable bonding layer.

2. The prestressed component according to claim 1, characterized in that: The controllable bonding layer is an epoxy resin layer, and the controllable bonding layer evenly fills the gap between the steel strand and the casing, and the thickness of the controllable bonding layer in the radial direction of the steel strand is 1.15-1.25 mm; The steel strand is obtained by twisting 19 wire rods, the nominal diameter of the steel strand is 21.8-28.6 mm, and the nominal area of ​​the steel strand is 313-532 mm 2 ;or, The steel strand is obtained by twisting 7 wire rods, the nominal diameter of the steel strand is 15.2-21.6 mm, and the nominal area of ​​the steel strand is 140-285 mm. 2 .

3. The prestressed member according to claim 1, characterized in that: The heating assembly includes a power source electrically connected to the steel strands.

4. The prestressed component according to claim 3, characterized in that: The steel strand comprises tensioning ends at both ends, the tensioning ends extend out of the sleeve and the concrete member, and the power source is a power source connected to the two tensioning ends of the steel strand.

5. The prestressed component according to claim 3, characterized in that: The prestressed tendons include at least two prestressed tendons arranged at intervals, wherein the steel strand of each prestressed tendon includes a tensioning end at one end and an anchoring end at the other end, wherein the anchoring end and the tensioning end extend out of the sleeve, the anchoring end is fixed inside the concrete member, and the tensioning end extends out of the concrete member; The heating assembly further comprises a conductive clamp, which is located inside the concrete member and connects the anchoring ends of adjacent steel strands; Wherein, the power supply is connected to the tensioning end of the adjacent steel strand.

6. The prestressed member according to claim 5, characterized in that: The conductive clamp is a U-shaped conductive clamp, and the conductive clamp is clamped and fixed between the anchoring ends of adjacent steel strands.

7. The prestressed member according to claim 3, characterized in that: The heating assembly further includes a variable resistor disposed in a connection circuit between the power source and the steel strand.

8. The prestressed member according to claim 1, characterized in that: The outer wall of the sleeve is formed with a plurality of longitudinal ribs distributed in an annular manner and a plurality of transverse ribs arranged at intervals along the axial direction of the sleeve. The longitudinal ribs are extended along the axial direction of the sleeve, the transverse ribs are extended along the circumferential direction of the sleeve, and each transverse rib connects the plurality of longitudinal ribs.

9. The prestressed member according to claim 1, characterized in that: The steel strand is obtained by twisting a plurality of wire rods, the troostitization rate of the wire rod is greater than or equal to 95%, the spacing between troostite lamellae is 50-70 nm, and the chemical composition of the wire rod includes, by mass percentage: C 0.85-0.91%, Si 0.3-1.0%, Mn 0.2-0.8%, Cr 0.15-0.45%, V 0.02-0.05%, S less than or equal to 0.008%, P less than or equal to 0.010%, N less than or equal to 0.004%, O less than or equal to 0.0020%, and the balance is Fe and other inevitable impurities.

10. The prestressed member according to claim 1, characterized in that: The steel strand is prepared by the following steps: Smelting molten steel to obtain target molten steel, wherein the chemical composition of the target molten steel includes, by mass percentage, C 0.85-0.91%, Si 0.3-1.0%, Mn 0.2-0.8%, Cr 0.15-0.45%, V 0.02-0.05%, S less than or equal to 0.008%, P less than or equal to 0.010%, N less than or equal to 0.004%, O less than or equal to 0.0020%, and the balance is Fe and other inevitable impurities; The target molten steel is cast into shape by continuous casting of small square billets to obtain an intermediate billet; Performing a high-speed wire rolling process on the intermediate billet to obtain a coil; The coil is immediately immersed in a salt bath tank for online salt bath isothermal treatment, and immediately after the treatment, the coil enters a heat preservation corridor for online aging treatment for temperature control, and after the treatment, it is cooled to room temperature to obtain the wire rod; The steel strand is prepared by sequentially subjecting a plurality of the wire rods to pickling, phosphating, drawing, stranding and stabilization processes; The salt bath temperature of the online salt bath isothermal treatment is 530-560° C., the salt bath time is 100-250 s, and the average cooling rate of the temperature control treatment is not higher than 0.2° C. / s.

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